Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
844,585
result(s) for
"COPPER"
Sort by:
Influence of the Interaction of Nickel and Copper with Ceria on Ethanol Steam Reforming over Ni-Cu-CeOsub.2 Catalysts
Catalysts of nickel-ceria, nickel-copper-ceria, and copper-ceria were explored with respect to their properties for hydrogen production through ethanol steam reforming (ESR). They were prepared by coprecipitation of the components within inverse microemulsions to achieve intimate contact between them, and the catalysts were characterized by N[sub.2] adsorption measurements, XRD, Raman spectroscopy, TPR, and XPS. The catalysts were tested for the ESR reaction, and they were regenerated with oxygen when significant deactivation took place, as occurred for the copper-containing systems. In contrast, the nickel–ceria catalyst exhibits a high activity and stability despite the formation of an important amount of carbon deposits during the course of the ESR test. The presence of nickel sites, which strongly interact with the ceria support, and which are affected by the presence of copper, and the limitation of copper for C-C bond breaking are invoked to explain the results obtained on the whole.
Journal Article
Born to run : a hidden tribe, superathletes, and the greatest race the world has never seen
McDougall reveals the secrets of the world's greatest distance runners--the Tarahumara Indians of Copper Canyon, Mexico--and how he trained for the challenge of a lifetime: a fifty-mile race through the heart of Tarahumara country pitting the tribe against an odd band of super-athletic Americans.
Book
Copper-Catalyzed Reaction of IN/I-Monosubstituted Hydrazones with CBrsub.4: Unexpected Fragmentation and Mechanistic Study
The copper catalyzed reaction of N-monosubstituted hydrazones with carbon tetrabromide leads to formation of expected dibromodiazadienes and unexpected dibromostyrenes. The experimental and theoretical study of the reaction revealed a key role of N-centered radicals, which can eliminate aryl radicals to form the corresponding dibromostyrenes. Alternatively, the oxidation of intermediate N-centered radicals by Cu(II) results in the corresponding diazadienes. These two reaction pathways are competitive directions of the reaction. Consequently, the reaction can be useful for the synthesis of both dibromostyrenes and rare dibromodiazadienes.
Journal Article
Electron transfer and reaction mechanism of laccases
Laccases are part of the family of multicopper oxidases (MCOs), which couple the oxidation of substrates to the four electron reduction of O₂to H₂O. MCOs contain a minimum of four Cu’s divided into Type 1 (T1), Type 2 (T2), and binuclear Type 3 (T3) Cu sites that are distinguished based on unique spectroscopic features. Substrate oxidation occurs near the T1, and electrons are transferred approximately 13 Å through the protein via the Cys-His pathway to the T2/T3 trinuclear copper cluster (TNC), where dioxygen reduction occurs. This review outlines the electron transfer (ET) process in laccases, and the mechanism of O₂reduction as elucidated through spectroscopic, kinetic, and computational data. Marcus theory is used to describe the relevant factors which impact ET rates including the driving force, reorganization energy, and electronic coupling matrix element. Then, the mechanism of O₂reaction is detailed with particular focus on the intermediates formed during the two 2e⁻reduction steps. The first 2e⁻step forms the peroxide intermediate, followed by the second 2e⁻step to form the native intermediate, which has been shown to be the catalytically relevant fully oxidized form of the enzyme.
Journal Article
Toxicity Mechanisms of Copper Nanoparticles and Copper Surfaces on Bacterial Cells and Viruses
Copper is a metal historically used to prevent infections. One of the most relevant challenges in modern society are infectious disease outbreaks, where copper-based technologies can play a significant role. Currently, copper nanoparticles and surfaces are the most common antimicrobial copper-based technologies. Despite the widespread use of copper on nanoparticles and surfaces, the toxicity mechanism(s) explaining their unique antimicrobial properties are not entirely known. In general, toxicity effects described in bacteria and fungi involve the rupture of membranes, accumulation of ions inside the cell, protein inactivation, and DNA damage. A few studies have associated Cu-toxicity with ROS production and genetic material degradation in viruses. Therefore, understanding the mechanisms of the toxicity of copper nanoparticles and surfaces will contribute to developing and implementing efficient antimicrobial technologies to combat old and new infectious agents that can lead to disease outbreaks such as COVID-19. This review summarizes the current knowledge regarding the microbial toxicity of copper nanoparticles and surfaces and the gaps in this knowledge. In addition, we discuss potential applications derived from discovering new elements of copper toxicity, such as using different molecules or modifications to potentiate toxicity or antimicrobial specificity.
Journal Article
Copper signalling: causes and consequences
Copper-containing enzymes perform fundamental functions by activating dioxygen (O
2
) and therefore allowing chemical energy-transfer for aerobic metabolism. The copper-dependence of O
2
transport, metabolism and production of signalling molecules are supported by molecular systems that regulate and preserve tightly-bound static and weakly-bound dynamic cellular copper pools. Disruption of the reducing intracellular environment, characterized by glutathione shortage and ambient Cu(II) abundance drives oxidative stress and interferes with the bidirectional, copper-dependent communication between neurons and astrocytes, eventually leading to various brain disease forms. A deeper understanding of of the regulatory effects of copper on neuro-glia coupling via polyamine metabolism may reveal novel copper signalling functions and new directions for therapeutic intervention in brain disorders associated with aberrant copper metabolism.
Journal Article